Optical elements for changing a distribution of light from a light source such that an illuminated area that is used as alignment marks or indications for visual recognition used in measuring devices, medical instruments, industrial robots and the like have been developed. Among such optical elements, there exist those in which divided portions of a cylindrical lens are combined (Patent Document 1) and those shaped in a pyramid with lateral surfaces having a cylindrical envelop (Patent Document 2).
However, a microlens array that is configured such that illumination distribution in an illuminated area formed on a surface becomes uniform to a satisfactory degree has not been developed conventionally.